The present invention generally relates to a phase lock circuit for a video signal. The present invention is more particularly directed to a circuit which generates a horizontal synchronizing signal in phase with a horizontal synchronizing signal reproduced from a laser video disc player.
A system including a laser video disc player and a personal computer mutually connected is known. In such a system, a video signal reproduced from the laser video disc player is supplied to a display device together with a video signal supplied from the personal computer. Generally, the video signal to be displayed is transmitted to the personal computer through a public telephone line.
A video signal used in a television set is defined by the IEA RS-170A standard, for example. According to the standard, one period of the video signal consists of four fields. A color frame is formed by one period of the video signal. On the other hand, a conventional laser video disc player has a still reproduction mode in which the video signal is reproduced for every two fields. In the still reproduction mode, as will be described in detail later, there is a large difference in phase between a horizontal synchronizing signal reproduced from the laser video disc player and a corresponding signal generated from a system clock of a phase locked loop for every two fields. Thus, it takes a long time to pull the horizontal synchronizing signal derived from the system clock phase into phase with the reproduced horizontal synchronizing signal. The difference in phase deteriorates a reproduced image in the horizontal direction of picture. Therefore, it is required to reduce the phase difference to zero rapidly and thereby stabilize images on the display.